There are a variety of systems and proposals for satellite television and data broadcasting or broadcasting over defined geographic or customer service areas. One proposal employs multiple spot-beam patterns to essentially cover an entire service area. However, there are requirements that complicate the operation of multiple spot-beam systems. One example is the “local-into-local” service, where the satellite operator must collect television broadcast signals from a specific television market area, called a “designated market area” or DMA (as defined by Nielsen Media Research Corp.), uplink these signals to the satellite via an uplink earth station, and then re-transmit these signals only to the subscribers within the original DMA and to no others. There are approximately 215 DMAs in the U.S., corresponding to approximately 1600 television signals. While the area of DMAs generally follow county lines, they are irregular in shape and vary in size. Since the spot-beams are nearly circular or oval in shape and limited in area, covering specific DMAs can become costly and require duplication in signal transmission because any one DMA may not be contained within a single spot-beam. That is, a spot-beam may contain one or more DMAs but it also may contain only parts of one or more DMAs, the remainder of the DMAs lying in adjacent beams. Thus, one or more DMAs may “straddle” two or more spot-beams. To serve a straddled DMA, the same TV signals must be transmitted in both spot-beams, decreasing the efficiency of the satellite and increasing its cost of operation.
A further complication may arise for an individual spot-beam serving DMAs containing many TV signals, such as heavily populated service areas surrounding New York City, which service area contains many DMAs and many TV signals. Because the high demand for TV signals from DMAs in this, and similar, service areas may exceed the spot-beam capacity, i.e., this spot-beam may “saturate,” either some DMAs must be omitted from the service or the data rate of the service must be reduced, limiting the utility of the service. Typically, the data rate for the service, i.e., the data rate per TV channel, must be limited to the value that meets the demand in the highest capacity spot-beam (such as serves the New York City service area). Spot-beams for other service areas, such as the vicinities of Chicago, Atlanta, or Los Angeles, may also saturate for the same reasons.
Accordingly, improvements in the design of satellite communications systems, antennas, and methods and systems for distributing spot-beams to cover a geographic area are desired in the art.